Radio transmitters are generally limited in total transmit power, a limit imposed by regulatory agencies or by the battery or power amplifier technology. This power limitation may result in reduced radio coverage. For example, as a wireless transmit/receive unit (WTRU) moves away from its base station, it typically increases its transmission power to maintain the same level of quality at the base station. The WTRU output power is controlled by the base station via a power control loop. When the WTRU reaches its maximum power and may no longer increase its power to maintain the signal quality desired at the base station, power scaling is applied. This may occur for example when the WTRU is close to cell-edge, or when the WTRU enters a region of deep signal fade.
Wireless communication systems keep evolving to meet the needs for providing continuous and faster access to a data network. In order to meet these needs, wireless communication systems may use multiple carriers for the transmission of data. A wireless communication system that uses multiple carriers for the transmission of data may be referred to as a multi-carrier system. The use of multiple carriers is expanding in both cellular and non-cellular wireless systems.
A multi-carrier system may increase the bandwidth available in a wireless communication system according to a multiple of how many carriers are made available. For instance, a dual carrier system may double the bandwidth as compared to a single carrier system and a tri-carrier system may triple the bandwidth as compared to a single carrier system and so on. In multi-carrier systems, the WTRU may transmit, for example, over two adjacent carriers. A power amplifier may be assumed to be common to the multiple carriers such that the total power is a shared resource between the multiple carriers. Methods and apparatus for power scaling for multi-carrier wireless terminals are desired.